Nixtamal and masa flour are used primarily for producing tortillas, taco shells and chips. The popularity of food products made from nixtamal has increased significantly in recent years thereby increasing the demand for nixtamal and the need for improved production processes.
Nixtamal is typically made commercially by the traditional method of cooking whole corn in a mixture of water and lime. The corn is cooked at a temperature below the boiling point for a period of time depending on the hardness of the corn. The corn is then allowed to steep for eight hours or more to loosen and degrade the pericarp.
The cooking liquor is then drained and the corn washed several times to remove the lime and other solubilized materials. The corn is then treated to remove the bran and separate any remaining pericarp. Thereafter, the washed and debranned corn is passed through a grinder to mill the corn to the selected particle size. The ground masa can be mixed with sufficient water to form a dough for making tortillas or other products. The ground masa can also be dried to produce a masa flour.
Conventional masa flour processes experience several disadvantages. For example, the time required for steeping places production limits on equipment and increases the space requirements for the manufacturing facility. In addition, the process produces large amounts of waste water which must be treated prior to disposal. The treating liquor contains large amounts of dissolved pericarp and soluble starches which cannot be ecologically discharged into water ways or municipal waste water systems. Generally, the manufacturing facility must bear the cost of treating the waste water prior to discharge.
In recent years a number of processes have been developed for improving the efficiency of nixtamal and masa flour production. Many of these processes attempt to shorten the cooking or steeping time or vary the concentration of additives to increase production rates. One example is disclosed in U.S. Pat. No. 5,558,898 to Sunderland. This patent discloses a process for producing masa flour where the whole grain is partially cooked in a hot alkaline solution to partially gelatinize the starch and loosen the bran. Thereafter, the grain is debranned, flash dried and milled.
Further developments in the production of masa and masa flour use ground corn or corn flour as the starting material instead of whole corn. These processes typically treat the ground corn with water at elevated temperatures to hydrate the corn in less time than the conventional steeping. An example of such a process is generally disclosed in U.S. Pat. No. 5,532,013 to Martinez-Bustos et al. In this process whole corn flour is mixed with lime and water and heated to 60.degree. to 95.degree. C. in a cooker-extruder to partially cook the mixture. The partially cooked mixture is then discharged through a die to a cooling chamber and thereafter extruded through a nozzle.
Other processes of producing masa from ground corn are disclosed in U.S. Pat. Nos. 5,395,637 and 5,401,522 to Reeg. The disclosed processes form a mixture of corn flour, water and lime and heat the mixture slightly above the gelatinization temperature and then cooled below the gelatinization temperature to only partially gelatinize the starch. The upper limit of the heating temperature is selected to carefully control the gelatinization of the starch.
The above-noted processes for producing nixtamal and masa flour have not completely overcome the deficiencies of the traditional masa production process. Accordingly, there is a continuing need in the industry for an improved process of producing nixtamal and masa flour.